1. Field
The present disclosure relates to a carbon molecular sieve membrane having excellent gas permeability and selectivity.
[Description about National Support Research and Development]
This study is made by the support of Global Advanced Technology Development (Energy and Resources Policy Division) of Korea Ministry of Trade, Industry and Energy Science under the supervision of Kocat Inc. (Research Management Specialized Organization: Korea Institute of Energy Technology Evaluation and Planning, Subject Identification No.: 1415136879).
This study is made by the support of Development of high performance olefin/paraffin hybrid sieve of Korea Ministry of Science, ICT and Future Planning (Research Management Specialized Organization: Future Leading Integrated Research Group Business, Subject Identification No.: Integrated Research Group 14-1-KRICT) under the supervision of KOREA RESEARCH INSTITUTE OF CHEMICAL TECHNOLOGY.
2. Description of the Related Art
In the petrochemical industry, ethylene/ethane or propylene/propane is a very important compound and forms a significantly large market all over the world. Such type of olefin/paraffin separation has been carried out by cryogenic distillation in general. However, the cryogenic distillation undesirably consumes a large amount of energy, and thus many attempts have been made to substitute it with energy-efficient membrane technology. In addition to this, there has been an increasing need for developing a gas separator membrane based on a Carbon Molecular Sieve (CMS), which is a membrane showing excellent quality in separating hardly separable gas molecules, such as O2/N2 or CO2/CH4, having a small difference in molecular size.
Such excellent gas separation quality of the CMS gas separator membrane is based on a combination of micropores (6-20 Å) having very high permeability with ultramicropores (≦6 Å) functioning as molecular sieve. Determination of the structure of such a CMS membrane is affected by various factors, including a polymer precursor, pyrolysis temperature, heating rate, pyrolysis time and pyrolysis condition. In general, as the free volume ratio of a polymer precursor is increased, the CMS shows higher separation quality. Referring to the treatment conditions, as the pyrolysis temperature is increased, the permeability tends to be decreased and the selectivity tends to be increased, while smaller micropores and ultramicropores are formed. In addition, as the heating rate is increased, the permeability tends to be increased and the selectivity tends to be decreased in general. It is thought that this may be closely related with the production rate of byproducts and firing of pores. In addition, as the pyrolysis time is increased, the selectivity tends to be increased but the permeability tends to be decreased (see, U.S. Pat. No. 8,911,534). Particularly, the pyrolysis temperature and polymer precursor play important roles in determining the quality of a CMS membrane. Koros Group (Georgia Institute of Technology, USA) has demonstrated that the separation quality of a CMS membrane can be determined by controlling the amount of oxygen during pyrolysis (Kiyono M, Williams P J, and Koros W J. Journal of Membrane Science 2010; 359(1-2):2-10, U.S. Pat. No. 8,486,179).